1. Field
The present application relates generally to wireless communications, and more specifically to methods and systems for enhancing uplink interference cancellation using Hybrid Automatic Repeat reQuest (HARQ) retransmissions.
2. Background
Wireless communication systems are widely deployed to provide various types of communication (e.g., voice, data, multimedia services, etc.) to multiple users. As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance.
In recent years, users have started to replace fixed line communications with mobile communications and have increasingly demanded great voice quality, reliable service, and low prices.
In addition to mobile phone networks currently in place, a new class of small base stations has emerged, which may be installed in a user's home and provide indoor wireless coverage to mobile units using existing broadband Internet connections. Such personal miniature base stations are generally known as access point base stations, or, alternatively, Home Node B (HNB) or femto cells. Typically, such miniature base stations are connected to the Internet and the mobile operator's network via DSL router or cable modem.
In future revisions of wireless standards such as Long Term Evolution (LTE), there is a need to support base stations of different powers (such as high-powered macro cells and lower-powered pico cells). Additionally, cells such as femto cells operate under “restricted association”, i.e., they only allow some user terminals (UTs) (e.g., user equipment, access terminal, mobile device, cellular device, etc.) to connect to them. For example, these UTs may belong to users who subscribe to a special access plan offered by the operator.
In a traditional homogeneous deployment, a UT typically connects to the cell with the highest geometry (i.e., signal to noise ratio). However, in a heterogeneous deployment, there are benefits in allowing the UT to connect to a weaker base station. For example, a UT may connect to the cell with the lowest path loss to minimize interference caused to the network, even though its geometry is lower. Similarly, in the case of restricted association, a UT may be forced to connect to a weaker geometry base station as it may not have permission to access the strongest geometry base station. In such instances in which the UT connects to a cell with lower geometry, the UT will generally experience a significant interference signal transmitted from the stronger base station.
Therefore, there is a need for communication techniques that enable efficient communication to a UT that is subject to a dominant interference signal that is transmitted by a different base-station. The desired systems and method should provide for interference cancellation such that the base station can offset the latency experienced by the UT awaiting decoding of data packets, referred to herein as the “victim” UT, with more efficient bandwidth usage and/or more efficient power consumption.